United Air Lines Flight 608
| United Air Lines Flight 608 | |
|---|---|
.jpg) A structurally identical Douglas DC-6 from United Air Lines |
|
| Accident summary | |
| Accident type | Structural failure from fire |
| place | about 1.5 miles southeast of Bryce Canyon Airport, Utah |
| date | October 24, 1947 |
| Fatalities | 52 |
| Survivors | 0 |
| Aircraft | |
| Aircraft type | Douglas DC-6 |
| operator | United Air Lines |
| Mark | N37510 |
| Departure airport | Los Angeles Airport |
| Destination airport | Chicago Municipal Airport |
| Passengers | 46 |
| crew | 6th |
| Lists of aviation accidents | |
On October 24, 1947, a Douglas DC-6 crashed on United Air Lines Flight 608 after a fire broke out on board. The crew of the aircraft, which was on a scheduled flight from Los Angeles Airport to Chicago Municipal Airport , decided to make an emergency landing at Bryce Canyon Airport ( Utah ). The machine hit about 2.4 km (1.5 statute miles ) southeast of the airport. All 52 inmates were killed. It was the first accident of this type of aircraft and at that time the second most serious aircraft accident in the USA.
Airplane and occupants
The Douglas DC-6 ( registration number : NC37510, c / n : 42875, s / n : 17) was delivered brand new to United Air Lines on March 21, 1947 and had completed 933 flight hours by the time of the accident.
There were six crew members and 46 passengers on board. Several celebrities were among the victims: Jack Guenther (senior editor of Look Magazine and former sports writer at United Press ) , Clement D. Ryan (former president of Montgomery Ward ), Gerard Barnes Lambert Jr. (son of Gerard Barnes Lambert, the Founder of the pharmaceutical company Warner-Lambert ) and Jeff Burkett ( Chicago Cardinals player ).
the accident
The plane took off at 10:23 MST in Los Angeles ( California ), rising to a cruising altitude of 5,790 meters (19,000 feet ). The scheduled flight to Chicago ( Illinois ) was carried out according to visual flight rules . At 12:21 MST, Captain Everett L. McMillen informed air traffic control of a fire in the underfloor hold , which could not be brought under control despite the use of fire extinguishers. Smoke penetrated the passenger cabin. The crew decided to make an emergency landing at Bryce Canyon Airport (Utah), which they were flying over at the time. The machine went into descent , turned on a westerly course and approached the airfield in a wide semicircle from the east. At 12:26 MST, the crew reported that they have a field landing would consider. A minute later, the pilots announced that they had the runway in sight.
When the approaching machine was about 20 miles (20 miles) from Bryce Canyon Airport, witnesses on the ground observed that it was dragging a bright plume of smoke that was increasingly darkened. Another witness who observed the approach about 15 miles from the airfield said she noticed flames on the underside of the fuselage. The plane hit about 1.5 miles (2.4 kilometers) south of Bryce Canyon Airport at 12:29 PM MST.
During the descent, the machine lost parts of the fuselage, the rear right outer door and parts of the inner right wing structure . The first wreckage of the aircraft was found around 42 kilometers (26 miles) from the point of impact.
Cause of accident
The wreckage was transported to Santa Monica and the rear fuselage section was partially reconstructed in the Douglas Aircraft Company plant there . It was found that the fire began in the so-called "Boiler Room", which, among other things, housed the fan heater for the air conditioning. From this underfloor compartment in the middle fuselage area, the fire spread within the wing root and in the cargo hold up to the level of the rear outer doors. The control cables running in the underfloor area were damaged by the fire. After another Douglas DC-6 had to make an emergency landing on November 11, 1947 due to a cabin fire, the airlines volunteered to stop using the type until the incident was cleared up. The origin of the fire in the aircraft that had crashed was also in the “boiler room”. The actual cause of the fire was initially unclear.
The Douglas DC-6 has four main tanks and four smaller "alternate tanks", one for each piston engine . During the climb , the engines are supplied with fuel from the "alternate tanks", which are then emptied. In cruise flight , the pilots turn off the fuel supply to the main tank. The crew who had not landed stated that they had pumped fuel from the two outer tanks into the two “alternate tanks” near the hull before the fire started. According to a United co-pilot, such pumping was also common practice on the flights he and Captain McMillen made. For safety reasons, however, the manufacturer did not plan to pump fuel into the “alternate tanks” and accordingly not documented it in the “Aircraft Operating Manual”. The Douglas Aircraft Company saw a danger that the "alternate tanks" could be damaged by overfilling if the pumping pressure continued. However, the manufacturer failed to warn against such a transfer in the operating manual.
Subsequent test flights, on which water was pumped between the "alternate tanks" as an experiment, revealed an additional, design-related problem: With continued pumping pressure, fuel was forced out of the vent valves of the maximally filled tanks. This ran along the fuselage and penetrated through an air inlet that was only three meters behind the vent valve of the inner right "alternate tank" to the fan heater of the air conditioning system, where it ignited. The burning fuel was distributed in the "Boiler Room" and could not be combated effectively with the fire extinguisher installed there . This discharged its contents directly into the fan heater and thus did not cover the entire "Boiler Room". The fire then spread further in the underground area.
As a consequence of the incidents, the Douglas Aircraft Company changed the position of the tank ventilation valves and revised the DC-6 operating manual.
Individual evidence
- ↑ a b c d e f g Official Investigation Report in English: CIVIL AERONAUTICS BOARD, Accident Investigation Report, United Air Lines Inc., Bryce Canyon, Utah, October 24 1947
- ^ Aviation Safety Network, Accident Summary NC37510, October 24, 1947 (English)
- ↑ Aerotransport Databank, Airframe Profile for DC-6 msm 42875
- ↑ Arial Visuals, Airframe Dossier, NC37510
- ↑ Passenger list of the flight (website can no longer be accessed)
- ↑ a b c d Official final report on both incidents in English: CIVIL AERONAUTICS BOARD, Accident Investigation Report, United Air Lines Inc., Bryce Canyon, Utah, October 24 1947 and American Airlines, Inc., Gallup, New Mexico, November 11 1947
Coordinates: 37 ° 41 ′ 6 ″ N , 112 ° 8 ′ 11 ″ W.